Add CSS Linear mode (#367)

* Add CSS Linear mode

Push hue fix up into interpolation plugins and provide a CSS compatible
linear interpolation plugin.

Fixes #366

* Fix lint

* Add INTERPOLATOR class override and bump version

* Docs: Add new interpolation topics and improve existing topics

* Add tests

coloraide/__meta__.py

@@ -193,5 +193,5 @@ def parse_version(ver: str) -> Version:
     return Version(major, minor, micro, release, pre, post, dev)
 
 
-__version_info__ = Version(2, 10, 0, "final")
+__version_info__ = Version(2, 11, 0, "final")
 __version__ = __version_info__._get_canonical()

coloraide/color.py

@@ -60,6 +60,7 @@
 from .filters.cvd import Protan, Deutan, Tritan
 from .interpolate import Interpolator, Interpolate
 from .interpolate.linear import Linear
+from .interpolate.css_linear import CSSLinear
 from .interpolate.continuous import Continuous
 from .interpolate.bspline import BSpline
 from .interpolate.bspline_natural import NaturalBSpline
@@ -140,6 +141,7 @@ class Color(metaclass=ColorMeta):
     PRECISION = util.DEF_PREC
     FIT = util.DEF_FIT
     INTERPOLATE = util.DEF_INTERPOLATE
+    INTERPOLATOR = util.DEF_INTERPOLATOR
     DELTA_E = util.DEF_DELTA_E
     HARMONY = util.DEF_HARMONY
     AVERAGE = util.DEF_AVERAGE
@@ -1030,7 +1032,7 @@ def interpolate(
         premultiplied: bool = True,
         extrapolate: bool = False,
         domain: list[float] | None = None,
-        method: str = "linear",
+        method: str | None = None,
         padding: float | tuple[float, float] | None = None,
         carryforward: bool | None = None,
         powerless: bool | None = None,
@@ -1049,7 +1051,7 @@ def interpolate(
         """
 
         return interpolate.interpolator(
-            method,
+            method if method is not None else cls.INTERPOLATOR,
             cls,
             colors=colors,
             space=space,
@@ -1382,6 +1384,7 @@ def alpha(self, *, nans: bool = True) -> float:
 
         # Interpolation
         Linear(),
+        CSSLinear(),
         Continuous(),
         BSpline(),
         NaturalBSpline(),

coloraide/interpolate/__init__.py

@@ -17,7 +17,6 @@
 import math
 import functools
 from abc import ABCMeta, abstractmethod
-from .. import util
 from .. import algebra as alg
 from .. spaces import HSVish, HSLish, Cylindrical, RGBish, LChish, Labish
 from ..types import Vector, ColorInput, Plugin
@@ -83,6 +82,7 @@ def __init__(
         extrapolate: bool = False,
         domain: Sequence[float] | None = None,
         padding: float | tuple[float, float] | None = None,
+        hue: str = 'shorter',
         **kwargs: Any
     ):
         """Initialize."""
@@ -100,6 +100,7 @@ def __init__(
         self._out_space = out_space
         self.extrapolate = extrapolate
         self.current_easing = None  # type: Mapping[str, Callable[..., float]] | Callable[..., float] | None
+        self.hue = hue
         cs = self.create.CS_MAP[space]
         if isinstance(cs, Cylindrical):
             self.hue_index = cs.hue_index()
@@ -469,6 +470,7 @@ def interpolator(
         extrapolate: bool = False,
         domain: list[float] | None = None,
         padding: float | tuple[float, float] | None = None,
+        hue: str = 'shorter',
         **kwargs: Any
     ) -> Interpolator:
         """Get the interpolator object."""
@@ -550,93 +552,6 @@ def process_mapping(
     return {aliases.get(k, k): v for k, v in progress.items()}
 
 
-def adjust_shorter(h1: float, h2: float, offset: float) -> tuple[float, float]:
-    """Adjust the given hues."""
-
-    d = h2 - h1
-    if d > 180:
-        h2 -= 360.0
-        offset -= 360.0
-    elif d < -180:
-        h2 += 360
-        offset += 360.0
-    return h2, offset
-
-
-def adjust_longer(h1: float, h2: float, offset: float) -> tuple[float, float]:
-    """Adjust the given hues."""
-
-    d = h2 - h1
-    if 0 < d < 180:
-        h2 -= 360.0
-        offset -= 360.0
-    elif -180 < d <= 0:
-        h2 += 360
-        offset += 360.0
-    return h2, offset
-
-
-def adjust_increase(h1: float, h2: float, offset: float) -> tuple[float, float]:
-    """Adjust the given hues."""
-
-    if h2 < h1:
-        h2 += 360.0
-        offset += 360.0
-    return h2, offset
-
-
-def adjust_decrease(h1: float, h2: float, offset: float) -> tuple[float, float]:
-    """Adjust the given hues."""
-
-    if h2 > h1:
-        h2 -= 360.0
-        offset -= 360.0
-    return h2, offset
-
-
-def normalize_hue(
-    color1: Vector,
-    color2: Vector | None,
-    index: int,
-    offset: float,
-    hue: str,
-    fallback: float | None
-) -> tuple[Vector, float]:
-    """Normalize hues according the hue specifier."""
-
-    if hue == 'specified':
-        return (color2 or color1), offset
-
-    # Probably the first hue
-    if color2 is None:
-        color1[index] = util.constrain_hue(color1[index])
-        return color1, offset
-
-    if hue == 'shorter':
-        adjuster = adjust_shorter
-    elif hue == 'longer':
-        adjuster = adjust_longer
-    elif hue == 'increasing':
-        adjuster = adjust_increase
-    elif hue == 'decreasing':
-        adjuster = adjust_decrease
-    else:
-        raise ValueError("Unknown hue adjuster '{}'".format(hue))
-
-    c1 = color1[index] + offset
-    c2 = util.constrain_hue(color2[index]) + offset
-
-    # Adjust hue, handle gaps across `NaN`s
-    if not math.isnan(c2):
-        if not math.isnan(c1):
-            c2, offset = adjuster(c1, c2, offset)
-        elif fallback is not None:
-            c2, offset = adjuster(fallback, c2, offset)
-
-    color2[index] = c2
-    return color2, offset
-
-
 def carryforward_convert(color: Color, space: str, hue_index: int, powerless: bool) -> None:  # pragma: no cover
     """Carry forward undefined values during conversion."""
 
@@ -776,19 +691,9 @@ def interpolator(
     elif powerless and is_cyl and current.is_achromatic():
         current[hue_index] = math.nan
 
-    # Normalize hue
-    offset = 0.0
-    norm_coords = current[:]
-    fallback = None
-    if hue_index >= 0:
-        h = norm_coords[hue_index]
-        norm_coords, offset = normalize_hue(norm_coords, None, hue_index, offset, hue, fallback)
-        if not math.isnan(h):
-            fallback = h
-
     easing = None  # type: Any
     easings = []  # type: Any
-    coords = [norm_coords]
+    coords = [current[:]]
 
     i = 0
     for x in colors[1:]:
@@ -814,16 +719,8 @@ def interpolator(
         elif powerless and is_cyl and color.is_achromatic():
             color[hue_index] = math.nan
 
-        # Normalize the hue
-        norm_coords = color[:]
-        if hue_index >= 0:
-            h = norm_coords[hue_index]
-            norm_coords, offset = normalize_hue(current[:], norm_coords, hue_index, offset, hue, fallback)
-            if not math.isnan(h):
-                fallback = h
-
         # Create an entry interpolating the current color and the next color
-        coords.append(norm_coords)
+        coords.append(color[:])
         easings.append(easing if easing is not None else progress)
 
         # The "next" color is now the "current" color
@@ -836,6 +733,7 @@ def interpolator(
 
     # Calculate stops
     stops = calc_stops(stops, i)
+    kwargs['hue'] = hue
 
     # Send the interpolation list along with the stop map to the Piecewise interpolator
     return plugin.interpolator(

coloraide/interpolate/bspline.py

@@ -10,10 +10,7 @@
 from .continuous import InterpolatorContinuous
 from ..interpolate import Interpolator, Interpolate
 from ..types import Vector
-from typing import Callable, Mapping, Sequence, Any, TYPE_CHECKING
-
-if TYPE_CHECKING:  # pragma: no cover
-    from ..color import Color
+from typing import Any
 
 
 class InterpolatorBSpline(InterpolatorContinuous):
@@ -80,36 +77,7 @@ class BSpline(Interpolate):
 
     NAME = "bspline"
 
-    def interpolator(
-        self,
-        coordinates: list[Vector],
-        channel_names: Sequence[str],
-        create: type[Color],
-        easings: list[Callable[..., float] | None],
-        stops: dict[int, float],
-        space: str,
-        out_space: str,
-        progress: Mapping[str, Callable[..., float]] | Callable[..., float] | None,
-        premultiplied: bool,
-        extrapolate: bool = False,
-        domain: list[float] | None = None,
-        padding: float | tuple[float, float] | None = None,
-        **kwargs: Any
-    ) -> Interpolator:
+    def interpolator(self, *args: Any, **kwargs: Any) -> Interpolator:
         """Return the B-spline interpolator."""
 
-        return InterpolatorBSpline(
-            coordinates,
-            channel_names,
-            create,
-            easings,
-            stops,
-            space,
-            out_space,
-            progress,
-            premultiplied,
-            extrapolate,
-            domain,
-            padding,
-            **kwargs
-        )
+        return InterpolatorBSpline(*args, **kwargs)

coloraide/interpolate/bspline_natural.py

@@ -7,11 +7,7 @@
 from .. interpolate import Interpolate, Interpolator
 from .bspline import InterpolatorBSpline
 from .. import algebra as alg
-from ..types import Vector
-from typing import List, Sequence, Any, Mapping, Callable, Dict, Type, TYPE_CHECKING
-
-if TYPE_CHECKING:  # pragma: no cover
-    from ..color import Color
+from typing import Any
 
 
 class InterpolatorNaturalBSpline(InterpolatorBSpline):
@@ -39,36 +35,7 @@ class NaturalBSpline(Interpolate):
 
     NAME = "natural"
 
-    def interpolator(
-        self,
-        coordinates: List[Vector],
-        channel_names: Sequence[str],
-        create: Type[Color],
-        easings: List[Callable[..., float] | None],
-        stops: Dict[int, float],
-        space: str,
-        out_space: str,
-        progress: Mapping[str, Callable[..., float]] | Callable[..., float] | None,
-        premultiplied: bool,
-        extrapolate: bool = False,
-        domain: list[float] | None = None,
-        padding: float | tuple[float, float] | None = None,
-        **kwargs: Any
-    ) -> Interpolator:
+    def interpolator(self, *args: Any, **kwargs: Any) -> Interpolator:
         """Return the natural B-spline interpolator."""
 
-        return InterpolatorNaturalBSpline(
-            coordinates,
-            channel_names,
-            create,
-            easings,
-            stops,
-            space,
-            out_space,
-            progress,
-            premultiplied,
-            extrapolate,
-            domain,
-            padding,
-            **kwargs
-        )
+        return InterpolatorNaturalBSpline(*args, **kwargs)

coloraide/interpolate/catmull_rom.py

@@ -7,11 +7,7 @@
 from .bspline import InterpolatorBSpline
 from ..interpolate import Interpolator, Interpolate
 from .. import algebra as alg
-from ..types import Vector
-from typing import Callable, Mapping, Sequence, Any, TYPE_CHECKING
-
-if TYPE_CHECKING:  # pragma: no cover
-    from ..color import Color
+from typing import Any
 
 
 class InterpolatorCatmullRom(InterpolatorBSpline):
@@ -29,36 +25,7 @@ class CatmullRom(Interpolate):
 
     NAME = "catrom"
 
-    def interpolator(
-        self,
-        coordinates: list[Vector],
-        channel_names: Sequence[str],
-        create: type[Color],
-        easings: list[Callable[..., float] | None],
-        stops: dict[int, float],
-        space: str,
-        out_space: str,
-        progress: Mapping[str, Callable[..., float]] | Callable[..., float] | None,
-        premultiplied: bool,
-        extrapolate: bool = False,
-        domain: list[float] | None = None,
-        padding: float | tuple[float, float] | None = None,
-        **kwargs: Any
-    ) -> Interpolator:
+    def interpolator(self, *args: Any, **kwargs: Any) -> Interpolator:
         """Return the Catmull-Rom interpolator."""
 
-        return InterpolatorCatmullRom(
-            coordinates,
-            channel_names,
-            create,
-            easings,
-            stops,
-            space,
-            out_space,
-            progress,
-            premultiplied,
-            extrapolate,
-            domain,
-            padding,
-            **kwargs
-        )
+        return InterpolatorCatmullRom(*args, **kwargs)